Tubes are often used, for example, in medical and pharmaceutical applications for storing products in the form of pastes, jellies, emulsions, liquids, foams, powders, etc. Typically the container body of such a tube is imprinted on its outer surface, for example, with a product name. However, subject to external influences the characteristics of the ink used for imprinting may alter. External influences may be chemical, mechanical and/or physical in nature. Furthermore, the tube container typically collapses when the product is dispensed unless air is allowed to pass into the tube container during dispensing.
To protect the imprint from external influences tubes are typically varnished after imprinting. Varnish is usually a combination of a resin, a thinner or solvent and additives such as photoinitiators and so on (http://en.wikipedia.org/wiki.Varnish) and comprises components that may migrate through the sheet material of the container body and contaminate the product even if only a thin layer of varnish is applied.
Often a laminate is used as sheet material for the container body of the tube, the laminate consisting of several layers adhered to each other. The laminate in particular comprises a carrier layer that is sandwiched between two thermoplastic layers as described in U.S. Pat. No. 3,660,194 A and WO 2010/135843 A1. The carrier layer usually constitutes a barrier layer, i.e. it has low permeability. Suitable materials for the carrier layer are for example aluminium, SiOx, AlxOy, ethylene vinyl alcohols (EVOH), cyclic olefin copolymer (COC) among others. In case of the carrier layer being an aluminium foil, an exemplary sheet material in form of a laminate is composed of the aluminium foil sandwiched between two thermoplastic layers with adhesive layers between the aluminium foil and each thermoplastic layer (i.e. thermoplastic layer—adhesive layer—aluminium foil—adhesive layer—thermoplastic layer). Polyethylene (PE), in particular low-density polyethylene (LDPE) may, for example, be used as material for the thermoplastic layers. The inner thermoplastic layer serves as protection of the product from the aluminium foil (or carrier layer of other material, respectively). The outer thermoplastic layer is optional. It is referred to WO 2010/135843 A1 for further possible sheet material compositions.
The sheet material is bent into the shape of a typically cylinder-like container body. Adjacent overlapping edges of the sheet material with overlapping barrier layer are connected by heat-sealing resulting in a longitudinal seam. After that an optional sheathing is applied to the outside of the wound and heat-sealed sheet material to cover the longitudinal seam of the overlapping region and to obtain a container body with an entirely smooth outer surface and with a more uniform wall thickness. The sheathing typically consists of thermoplastic material. The sheathing is provided by way of extrusion, in particular extrusion coating (see U.S. Pat. No. 3,660,194 A, http//:en.wikipedia.org/wik/Plastics_extrusion).
After provision of the sheathing the container body is cut into its final length and a tube head is placed onto the container body by means of injection moulding as described in U.S. Pat. No. 3,660,194 A and WO 2010/135843 A1.
The sheathing may consist of several layers with the layers being identical with respect to their base material, the base material according to the state of the art for example being a thermoplastic polyester elastomere (TPE-E/TPC) base material (see WO 2010/135843 A1). The smooth outer surface of the sheathing can be used for imprinting (see WO 2010/135843 A1). The imprint is, however, not protected against external influences. As an alternative, WO 2010/135843 A1 discloses the use of a coloured sheathing or to employ a sheathing that consists of several layers wherein the layers contain different pigments or dyes.
Patent application DE 10 2009 051 071 A1 discloses a method for manufacturing a tube container body, wherein a sheet material is bent and longitudinal edges of the sheet material are connected by means of butt welding, the longitudinal edges being adjacent to each other but not overlapping after bending. Thus, the bent and welded sheet material has a smooth outer surface with uniform wall thickness. To secure and unburden the longitudinal seal that connects the edges a sheathing is provided on the outer surface by extrusion, such that the longitudinal seal can withstand also extreme mechanical forces or pressures. Such extreme mechanical forces or pressures can occur when manually squeezing the product out of the tube or when bending or curling the container body. The layer of the layered sheet material that is adjacent to the sheathing may be imprinted on its outside with the sheathing being transparent. The layered sheet material consists of two layers of PE with a layer of aluminium or EVOH sandwiched between the two PE layers. The sheathing also consists of PE. The sheathing may consist of several layers with one layer for example acting as adhesive layer.
Nowadays pre-imprinted laminates are usually employed that are manufactured by reverse printing. With reverse printing the imprint is applied to the inner surface of the outermost layer of the laminate. Reverse printing requires a lamination process for the production of the imprinted laminate. Reverse printing cannot be achieved by extrusion or extrusion coating. A sheathing is not provided as there is no need to protect reversely printed laminates from external influences.